Minimally invasive procedures are preferred over conventional techniques wherein the patient's body cavity is opened to permit the surgeon's hands access to internal organs. Thus, there is a need for highly controllable, yet minimally sized, medical instruments to facilitate imaging, diagnosis and treatment of tissues which may lie deep within a patient, and which may be accessed via naturally-occurring pathways, such as blood vessels, other body passages or lumens, via surgically-created wounds of minimized size, or through combinations thereof.
Currently known minimally invasive procedures for the treatment of cardiac and other disease conditions employ both manually and robotically controlled instruments, such as steerable catheters, which may be inserted transcutaneously into body spaces such as the thorax or peritoneum, transcutaneously or percutaneously into lumens such as the blood vessels, through natural orifices and/or lumens such as the mouth and/or upper gastrointestinal tract, etc. Such devices are well suited for performing a variety of minimally invasive diagnostic and therapeutic procedures.
When manually controlling an elongate instrument, such as a steerable catheter having a proximal end handle, the physician operator (while grasping the handle) can axially push on the proximal end of the catheter and attempt to tactilely “feel” the catheter distal end make contact with pertinent tissue structures located deep in the patient's body, such as the walls of the heart. Some experienced physicians attempt to mentally determine or gauge the approximate force being applied to the distal end of a catheter due to contact with tissue structures or other objects, by interpreting the loads they tactilely sense at the proximal end of the inserted catheter with their fingers and/or hands. Such an estimation of the force, however, is quite challenging given the generally compliant nature of many minimally-invasive instruments, associated frictional loads, dynamic positioning of the instrument versus nearby tissue structures, and other factors.
Robotically controlled catheters have a proximal interface coupled with an instrument driver comprising, for example, one or more motors that are selectively actuated to induce intra-body navigation of the distal portion of the catheter in response to commands input by an operator at a master input station or using some other device that may be located remotely from the patient. Thus, even the most gifted of operator physicians would be unable to gauge forces applied to the distal end of the catheter through tactile feel at the proximal end.
Regardless of the manual or electromechanical nature of the driving mechanism for a diagnostic or interventional catheter, the operator performing the procedure would prefer to have accurate, timely information regarding the forces experienced at the distal portion of the catheter, such as loads applied by or to the catheter from adjacent tissues and other objects.